1. Field of the Invention
The present invention relates to microbial-resistant medical devices and, more particularly, to a voice prosthesis having a valve seat which retards growth of microorganisms.
2. Prior Art
There are several options for restoring speech to patients who have had their larynx removed. One procedure is to surgically create a puncture or fistula between the trachea and the esophagus. A tracheoesophageal voice prosthesis containing a one-way valve such as a BLOM-SINGER® voice prosthesis is inserted into the tracheoesophageal fistula. The one-way valve protects the airway during swallowing but opens under positive pressure from the trachea. The voice prosthesis, thus, permits a patient to divert air from the lungs into the esophagus and out through the mouth. Speech is created during passage of air through the upper part of the esophagus.
The voice prosthesis maintains the patency of the fistula, transfers air from the trachea to the esophagus for voice production and prevents esophageal leakage into the trachea during swallowing. The oral cavity which extends into the throat can have a high microbial population. The prosthesis, being in contact with moisture in a warm, dark, nutrient rich environment, is subject to growth of commonly found micro-organisms, typically Candida, on the valve, valve seat and the retaining flange. The microbial growth on and into the soft silicone resin can interfere with function of the valve and can cause the valve seat to warp and the valve to leak.
A voice prosthesis has been developed that can remain in place in the tracheoesophageal fistula for months, depending on the patient and conditions of use. The patient can confidently use the prosthesis for longer periods than the non-indwelling voice prosthesis. The longer dwelling voice prosthesis is not removable by the patient. Trips to a health care specialist to remove and replace the prosthesis are greatly extended providing increased comfort and lower cost to the patient.
Blom, in U.S. Pat. No. 4,435,853 discribes a soft voice prosthesis for use over an extended period of time. This voice prosthesis does not include the use of an antimicrobial agent.
Persson, in U.S. Pat. No. 5,314,470 discloses a soft voice prosthesis that includes a rigid stiffening ring 14 inserted into a groove in the soft body of the prosthesis.
U.S. Pat. No. 5,578,083 issued Nov. 26, 1996, discloses the use of a stiff cartridge to support the soft silicone prosthesis and to provide a seat for the valve. However, microbial growth still proceeds to a point at which the valve can not be reliably sealed.
Although the rigid valve seat designs reduce microbial ingrowth into the valve seat material, they do not retard microbial growth. Leaking can be due to distortion of the valve body adjacent to the seat of the valve and to microbial growth on the seat.
Relevant prior art includes U.S. Pat. Nos. 3,932,627, 4,054,139, 4,483,688, 4,563,485, 4,581,028, 4,603,152, 4,612,337, 4,615,705, 5,019,096, 5,567,495, 5,624,704, 5,772,640, 5,902,283, 6,083,208 and 6,106,505.